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PC Ground Station 5 m/s vertical "limit" - up AND down?

Discussion in 'DJI Ground Station' started by isky172, Jul 25, 2014.

  1. isky172

    Jul 9, 2014
    Likes Received:
    I did a PC Ground Station (GS) flight today up to ~700 meters. All was fine on the way up, taking just about 4 minutes to reach altitude. As far as remarkable settings for my flight, the one I'm concerned with is the vertical speed limit setting. In PC GS you can set limits on speed - both vertical and horizontal. Horizontal max is 25 m/s (which a P2 would never reach, of course) and the vertical is 5 m/s (whether or not a loaded P2 could reach 5 m/s on the "up" is unknown.) I set my vertical limit to the max allowed by the GS application - I chose 5 m/s. I did this in order to climb as fast as possible to my intended altitude and give as much time as the quad needed to descend at its default "slower"/"built-in" rate of 2 m/s max. A link to the PC GS screen wherein I chose this vertical setting is below. However, in the graphic take a note that the text indicator/explanation of that field says "Vertical speed limit, between 0.5 and 5.0 m/s." I didn't quite catch the fact there is no mention of ascent/descent in this description. Chi-English usually keeps me from paying too much attention to DJI instructions/indicators;

    (Also available here: https://drive.google.com/file/d/0B0cCpcJFBbmDXzJXUlpCelFRZXc/edit?usp=sharing)

    Like a lot of people (I suspect) I've always been under the assumption that the maximum "descent" speed (since a firmware update some time ago) was 2 m/s - in order to avoid the dreaded Vortex Ring State (VRS). So I figured I was plugging in a 5 m/s climb and a default 2 m/s descent. I.e., I assumed the "5 m/s" I entered into my flight plan was for the ascent stage only.

    So the flight took off and away it went as expected. Nothing out of the ordinary happened. Also, on the way down I didn't notice anything crazy. As it came within sight I just landed and packed up my things. But once at home, I watched the video. Horrifically, it appears I nearly lost everything to a crash. Take a look at this link - http://youtu.be/hkMcngDEPxo. At about 2:30 to 2:45, it appears the P2 nearly "lost it". The "tilt" is quite significant and the gimbal had no chance of keeping up.

    So for those interested in commenting, is this a near miss of VRS? A VRS half-entry, so to speak? If not, what could have caused it to tip over so drastically in-flight/during the descent? Also, does anyone else have an experience that would lead them to believe/confirm that the default 2 m/s descent maximum for the P2 is overridden when flying a GS flight plan?

    Thanks - as always.

    Attached Files:

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